1. Field of the Invention
This invention relates to oven controllers for controlling temperature, time, and duty cycle. More specifically, it relates to the inputting of data to microprocessor based digital electronic circuits.
Over the years conventional home cooking ovens have employed simple electromechanical control devices generally comprising a rotatable knob to set a selected temperature. Another rotatable knob was frequently provided to provide a timing function either to provide a audible signal denoting completion of the selected period of time or to automatically turn off power to the oven at that time.
With the advent of the microwave oven, the problem of controlling the operation became somewhat more complex. That is, in the microwave ovens it is desirable to vary the duty cycle of the magnetron which produces the microwaves for cooking for different comestible or for defrosting or reheating as opposed to cooking. Initially this was accomplished by referring to a cookbook provided by the oven manufacturer to obtain a listed duty cycle and then by setting a dial according to the listed duty cycle.
More recently microwave oven controllers have utilized microprocessor based digital electronic circuits in which control data or parameters such as time, temperature and duty cycle are set by appropriate commands entered through a capacitive touch plate or keyboard. These have proven to be very effective however such capacitive touch plates and associated interface apparatus are inherently relatively expensive. It has been proposed to use dial or slide controlled digital encoders, for example, a wiper rotated by a dial so that it can make contact with different weighted lines on a circuit board to input cook data to a microprocessor based controller however this approach is not only relatively expensive compared to electromechanical timers and the like it also uses more control lines of the microprocessor than is desired. Another disadvantage of employing digital encoders is that in order to provide the necessary contacts that would be required in a full dial rotation of 360 degrees, the device would be either too large or the individual conductive lines would have to be too small to be practical for production. Thus there remains a need to provide the same control function for less cost so that a greater number of households can afford such ovens. That is, there is a need for an electronic controller which is economically competitive with electromechanical devices such as timing motors while performing comparable or improved functions.